of milan



Nov. 1, 1927. 1,647,563

L. EMANUEL] HIGH TENSIQN ELECTRIC CABLE Filed April 26, 1926 [La/ 71 manual L'UIGI EMANUELI, OF MILAN, ITALY,

tense-3 PATENT OFFICE.

ASSIGNOR T PIRELLT & 0., OF MILAN, ITALY. A. FIRM. r

HIGH-TENSION ELECTRIC CABLE Application filed Apri'l 2s, isaaseriai No. 104,722, and in Italy May s, 1925.

' The high tensionelectric cables now in use generally consist of one or more conductors insulated with paper or textile material which has been saturated with oil and cov- 5 ered with a lead sheath.

There are particular types of cables that contain a cavity on the inside of the conductors, or between the conductor and insulation, which cavity remains filled with oil.

cables are installed are then furnished with elevated containers also filled with oiland communicating with the cavity of the cable, thereby keeping the insulation always perfectly saturated even when, at low temperature, the oil contracts and forms, in the dielectric, empty spaces-that is, points of easy perforation.

The above mentioned cavity situated inside the conductor causes difficulty in the construction of the joints and other accessories (terminal boxes, oil reservoirs, etc.) rendering them complicated and costly. Moreover, the cavity happens to be located where the electric stress is greatest, whereas the oil itself has a dielectric strength less than that of saturated paper.

The present invention refers to. a type of cable particularly suitable for saturation with light oils and for systems furnished with oil feeding reservoirs in which the above mentioned difliculties are mostly eliminated or greatly reduced by the utilization of the cavity situated between the insulation and the lead sheath, that is, Where the electric stress has a lower value.

In the accompanying drawing, the single figure is a cross-section of a cable embodying the preferred structural features of 'the invention and including, in this instance, three conductors, though it is to be understood that no limitation to that particular number is contemplated.

According to the illustrated embodiment,

1 indicates the three conductors mentioned above, these conductors being provided'each with a covering or'wrap'ping 2- of oil-saturated pa er or textile material and being suitably tled or bound together. The unit thus formed as a covering layer 7 of insulation wrapped or wound around it, over which, in turn, a lead sheath 5 is fitted, and it is this sheath 5 which resents the most important features of my invention.

The electric lines or systems in which such As will be seen in the drawing, the inner surface of the sheath is grooved or channelled to form a multiplicity of ribs 6 which are approximately -T-shaped in cross-sectlons; that is to say, their free outerportions or cross-pieces are substantially flat and have a much greater width than theirinner portrons or stems, the separating spaces or channels between adjacent ribs having of necessity the reverse formation in point of crosssectional shape and relative dimensions. The outer portions of the ribs contact directly with the insulating layer 7, but because of their width they are not liable to 'cut into said layer if the cable should be subected to crushing forces; and for the same reason, electric stresses are avoided because the edges of the said rib portions may be, and preferably are, rounded slightly. Furthermore, the aforesaid portions are in continuous contact with, and cover substantially the "entire surface of, the insulation. The oil, of course, flows freely through the previouslymentioned spaces or channels between the ribs, which channels are nearly closed by the outer portions of the ribs due to their peculiar formation.

I claim'as my invention .1. Ahigh tension electric cable, comprising conducting means, insulatibn surroundin the same, and a lead sheath enclosing said insulation and having spaced, longitudinally-extending ribs formed on its inner surface, the free outer portions of which contact directly with the surface of the insulation and are considerably enlarged with relation to their inner portions; the'spaces begween adjacent ribs constituting oil channe s.

2. A high tension electric cable, comprising conducting means, insulation surroundnally-extending ribs formed on its inner $111- face, the free outer portions of which contact directly with-the surface of the insulation and are considerably enlar ed with relation to their inner portions an are rounded at their edges; the spaces between adjacent ribs constituting oil channels.

4. A high tension electric cable, according to claim 1, in which the ribs are approximately T-sha ed in cross-section, thestems :of the Ts being integrally connected to the lead' sheath."

Y 5. A high tension ele'ctric cable, according to claim 1, in which the ribs are approxi mately' T-shaped in cross-section, the crosspieces of the Ts contacting with the surface of the insulation and having their edges rounded; and the stems of, the Ts being inenlarged and projecting laterally toward a each other 'so as to nearly close such passages.

In testimony whereof I aflix my signature.

LUIGI EMANUELI. 

